It is typically desirable to implement power supply systems in a manner that is suitable to achieve optimal efficiency. As an example, efficient power supply systems that generate DC power from a battery can extend the operating life of the battery. Some power supply applications can include operating with a variable load over a long duration of time. For example, in a utility monitoring application and/or an application that includes remote sensors, battery life can be intended to last over a period of years (e.g., 15 to 20 years). In such applications, the circuits to which the power supply provides power are in an idle or shutoff mode most of the time, such that the only system that is operating can be a supervisory timing system (e.g., a real-time clock). Periodically, the circuit systems can be briefly switched to an operating mode to perform a function, after which the circuits can return to the idle or shutoff mode. During the idle or shutoff mode, the load can draw very low current, such as between approximately 0.5 micro-amps (μA) and 1 μA. Reducing the current draw in such idle or shutoff mode in such applications can extend the life of the battery for a year or more.